The present invention relates to a method and apparatus for replacing in-ground hydraulic elevator cylinder casings.
A hydraulic elevator shaft cylinder is typically made of steel and is installed in a bored hole in the ground. The cylinder is therefore exposed to soil and ground water. As a result, corrosion will occur and the cylinder must eventually be replaced. Since the cylinder is installed below ground, within an elevator hoistway, and typically beneath a building, replacement of the corroded cylinder involves substantial difficulty and expense.
Various proposals have been made in the past for either reducing the corrosion problem or for reducing the problems inherent in replacing corroded cylinders. U.S. Pat. Nos. 4,983,072 of Bell, Jr, U.S. Pat. No. 5,076,146 of Bialy, U.S. Pat. Nos. 5,226,751, and 5,501,299 of Holmes all related to methods for protecting the outer surface of a submerged cylinder from corrosion, and do not suggest any method or apparatus for replacing the cylinder if and when it fails. Other methods and devices have been proposed in the past for retrofitting hydraulic lift cylinders, such as U.S. Pat. No. 5,860,491 of Fletcher. This patent describes a system and method for retrofitting a low pressure high volume lift system which involves installing a new cylinder inside the old cylinder, which is left in place. U.S. Pat. No. 5,709,286 of Mead describes another system in which a new lift assembly is installed directly within an existing in-ground cylinder. Thus, the old cylinder casing is not removed in either the Mead or Fletcher system.
Removing an existing, elongated cylinder in an enclosed field condition is a most difficult undertaking, so much so that the U.S. Government awarded a specialty contract (resulting in U.S. Pat. No. 5,307,386 of Chaves et al.) to develop a device for removing elongated coolant pumps suspended under steam generators within containment vessels in power plant switch limited access space. This patent is applicable only to the particular field described, specifically removal of large elongated pump motors suspended beneath a steam generator, and would not work in an elevator hoistway, or an unstable earthen bore hole. However, it does serve to demonstrate the need for devices to remove equipment with limited access space.
The current method used to remove an elevator hydraulic jack cylinder casing is to first suspend the elevator car from the top of the hoistway with a suitably strong beam placed on the roof of the building above the elevator shaft. In order to do this, a hole must first be cut through the building roof, and a chain with a hook or cable snatch block is then suspended from the beam into the elevator shaft. The elevator car is then hoisted up to the top of the elevator shaft with a chain fall suspended from the hook or snatch block. A winch device is then mounted within the elevator pit and a line is then affixed to a snatch block suspended from the bottom of the elevator car. This winch line is then used to lift the old, corroded elevator hydraulic jack cylinder casing out of the ground. This method often creates problems, such as spillage of hydraulic fluid, or cave-in of the shaft hole as the old cylinder casing is withdrawn from the hole. Also, the elevator car carriage is subject to racking/misalignment due to the weight of the hydraulic cylinder casing suspended from its bolster channels (under the elevator car). Under this current practice, the shaft hole must typically be pre-drilled, and thereafter, the new or replacement elevator hydraulic cylinder casing is installed using the chain winch suspended from the elevator car as a lifting device. This method is both time-consuming and expensive.
It is an object of the present invention to provide a new and improved apparatus and method for removing and replacing in-ground elevator hydraulic cylinder casings.
According to one aspect of the present invention, a method of removing and replacing an in-ground elevator hydraulic cylinder casing is provided, which comprises the steps of:
loosening an elevator hoistway floor and subsoil surrounding an in-ground elevator hydraulic cylinder casing to leave a gap around the casing;
centering a shoring sleeve of larger diameter than the in-ground hydraulic cylinder casing in an elevator hoistway above the floor of the hoistway centered on the in-ground cylinder casing;
lowering the shoring sleeve into the gap around the cylinder casing and forcing it down until it surrounds the entire outer surface of the casing to a depth below the lower end of the casing;
pulling the cylinder casing upwardly into the hoistway and disposing of the extracted cylinder casing; and
lowering a new hydraulic cylinder casing into the shoring sleeve.
In an exemplary embodiment of the invention, the method includes the steps of erecting a temporary hoist tower within an elevator hoistway to extend upwardly from the bottom of the hoistway in alignment with the in-ground elevator hydraulic cylinder casing, and mounting a drive assembly on the temporary hoist tower above the buried hydraulic cylinder casing. The drive assembly is then used to force the shoring sleeve downwardly to surround the hydraulic cylinder casing, and is then attached to the buried cylinder casing and used to lift the cylinder casing from the ground. The drive assembly may be a power winch or a hydraulic jack, or both a power winch and a hydraulic jack applied in unison where large frictional forces are to be overcome.
According to another aspect of the present invention, an apparatus for removing an old elevator hydraulic cylinder casing from the ground and replacing it with a new hydraulic cylinder casing is provided, which comprises a vertical tower having a lower end for mounting on the floor of an elevator hoistway centered over an in-ground hydraulic cylinder casing and extending vertically upwardly from the floor, a head plate slidably mounted on the tower for vertical movement up and down the tower, a releasable locking device for releasably securing the head plate at a selected height on the tower, the head plate having a downwardly facing attachment device for securing the head plate to a shoring sleeve or cylinder, and a pressing and lifting assembly for forcing the head plate downwardly along the tower to move a shoring sleeve or cylinder attached to the head plate to submerged, in-ground position below the floor of the elevator hoistway, and for lifting the head plate upwardly to lift an old cylinder casing from an in-ground position to a removed position spaced above the floor of the elevator hoistway.
In an exemplary embodiment of the invention, a beam is slidably mounted on the tower above the head plate, and a releasable locking device is provided for releasably locking the beam at a selected position on the tower, and at least one hydraulic jack may be mounted between the head plate and beam for lowering the head plate relative to the beam. A hydraulic jack may also be mounted between the lower end of the tower and the head plate for lifting the head plate in order to exert lifting force on an attached in-ground cylinder casing. A cable winch assembly may be provided for assisting in the lifting procedure, including a winch secured near the base of the tower and a cable and pulley assembly secured to the winch. Pulleys may be secured on the opposite side of the tower to the winch and to the top of the head plate.
The method and apparatus of this invention avoids the need to use an existing elevator car as a lifting anchor in replacing of old hydraulic cylinder casings, and thus avoids the risk of racking or misalignment of the car. The method involves installation of a shoring sleeve around the old cylinder casing prior to removal, thus avoiding or reducing the risk of the bore caving in before a new cylinder casing is installed. This method and apparatus also minimizes leakage of hydraulic fluid to the surrounding sub-soil as the old casing is removed.